jsp页面该如何刷新验证码

Posted 2023-05-11

tags:

篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了jsp页面该如何刷新验证码相关的知识，希望对你有一定的参考价值。

我的验证码是用servlet写的，代码如下

点击图片后，提示说yzmServlet没有定义，求正确写法

（1）jsp代码：
<img id = "img_authcode" src="$ctx/account/authcode" /><a href="javascript:;" onclick="javascript:document.getElementById('img_authcode').setAttribute('src', '$ctx/account/authcode?' + Math.random())">换一换</a>

（2）java代码（该代码为我自己框架代码，跟servlet写法不一样的我都给你注释了）：
public View authcode() throws IOException
HttpServletResponse response = PuffContext.getResponse();//获取response
response.setContentType("image/jpeg");
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
String authCode = AuthCodeUtil.getRandom(4); //获取验证码，代码在下面(3)
System.out.println("生成随机码：" + authCode);
PuffContext.getSession().setAttribute("session_authcode", authCode);//把该验证码存储在session
ServletOutputStream output = response.getOutputStream();
AuthCodeUtil.draw(output, authCode);
output.flush();
output.close();
return ViewFactory.nullView();//返回null

(3)///////////////////////////下面为生成验证码类////////////////////////////////////

public class AuthCodeUtil
private final static Random random = new Random();
// 随机字体样式
private final static int[] fontStyle = Font.HANGING_BASELINE, Font.ITALIC, Font.LAYOUT_LEFT_TO_RIGHT, Font.LAYOUT_NO_LIMIT_CONTEXT,
Font.LAYOUT_NO_START_CONTEXT, Font.LAYOUT_RIGHT_TO_LEFT ;

/**
* 画随机码图
*
* @param out
* @param width
* @param height
* @throws IOException
*/
public static void draw(OutputStream out, String value) throws IOException
int width = 80, height = 30;
BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics2D g = (Graphics2D) bi.getGraphics();
g.setColor(Color.WHITE);
g.fillRect(0, 0, width, height);
g.drawRect(1, 1, width - 2, height - 2);
for (int i = 0; i < 10; i++)
g.setColor(randColor(150, 250));
g.drawOval(random.nextInt(110), random.nextInt(24), 5 + random.nextInt(10), 5 + random.nextInt(10));

int n = (int) (Math.random() * 6);
Font mFont = new Font("Arial", fontStyle[n], 23);
g.setFont(mFont);
g.setColor(randColor(10, 240));
g.drawString(value, 10, 21);// 随机数,水平距离,垂直距离
ImageIO.write(bi, "png", out);

private static Color randColor(int fc, int bc) // 给定范围获得随机颜色
if (fc > 255)
fc = 255;
if (bc > 255)
bc = 255;
int r = fc + random.nextInt(bc - fc);
int g = fc + random.nextInt(bc - fc);
int b = fc + random.nextInt(bc - fc);
return new Color(r, g, b);

public static void main(String[] args) throws IOException
FileOutputStream out = new FileOutputStream("d:\\aa.png");
draw(out, getRandom(4));

public static String getRandom(int size) // 随机字符串
char[] c = '1', '3', '5', '6', '7', '8', '9' ;
StringBuffer sb = new StringBuffer();
for (int i = 0; i < size; i++)
sb.append(c[Math.abs(random.nextInt()) % c.length]);
return sb.toString();

参考技术A

我从头到尾说一遍吧

通过一个serlet绘制验证码，如DispCodeServlet

public class DispCodeServlet extends HttpServlet
public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException

  response.setHeader("Pragma", "No-cache");
  response.setHeader("Cache-Control", "no-cache");
  response.setDateHeader("Expires", 0);
  Random random=new Random();
  int length =5;
  String checkcode="";
  char code;
  int number;
  for(int i=0; i<length;i++)
   number=random.nextInt(26);
   if(number%2==0)
    code=(char)('0'+(char)(number%10));
   else
    code=(char)('A'+(char)(number%26));
   checkcode+=code+"";

  int width=(int)Math.ceil(length*12.5),height=22;
  BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
  Graphics g=image.getGraphics();
  g.setColor(Color.WHITE);
  g.fillRect(0, 0, width, height);
  g.setColor(Color.GRAY);
  g.drawRect(0,0,width-1,height-1);
  for(int i=0;i<25;i++)
   int x1=random.nextInt(width);
   int y1=random.nextInt(height);
   int x2=random.nextInt(width);
   int y2=random.nextInt(height);
   g.setColor(Color.GRAY);
   g.drawLine(x1,y1,x2,y2);

  g.setColor(Color.BLUE);
  g.setFont(new Font("Arial",Font.BOLD|Font.ITALIC,16));
  g.drawString(checkcode,5,18);
  HttpSession session=request.getSession();
  session.setAttribute("rand", checkcode);
  g.dispose();
  ImageIO.write(image, "JPEG", response.getOutputStream());

public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException

  doGet(request,response);

在jsp页面中使用画验证码，如下

然后在javascript中写入refresh()方法

function refresh()
document.getElementById("cc").src = "DispCodeServlet?a="
+ Math.random();

参考技术B <label>验证码</label><input id="code" type="text"/ maxlength="4" tabindex="3"><img id="checkCode" src="imgcode.jsp?random_mark=1111" width="83" height="24" onclick="javascript:changeCode();"/>

imgcode.jsp就是输出的一个验证码，然后changeCode是个js函数，点一下就更换random_mark=1111 这个的值，从而达到刷新的效果。希望采纳参考技术C this.src=你能访问到serlvet的路径；最好在这个路径的后面放一个随机数Math.random()；不需要接收这个参数，这只是告诉后台，这个路径跟你原来的是不一样的。本回答被提问者采纳参考技术D 连接后面加编号，每次刷新编号+1

动态生成能够局部刷新的验证码AJAX技术---看了不懂赔你钱

在开发JavaWeb应用时，动态生成能够局部刷新的验证码是一项必须的功能，在这里我们将会详细的讲解如何实现这一功能。

一、涉及技术

该功能需要用到AJAX异步传输技术，这样能保证在点击“看不清，重新获取验证码”按钮时，能够不刷新页面其它内容而局部刷新验证码图片内容。

还需要用到Servlet技术，这里会在Servlet的GET方法中通过Java内置的画图工具绘制一个验证码图片，可以在HTML的<img/>标签中的src属性获取缓存图片资源。

二、各个页面及代码

1.index.html，是一个简单的表单，上面仅有简单几项内容，AJAX异步传输技术也在上面体现，代码中有详细注释。

[html] view plain copy

print?

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8"/>
<title>验证码测试</title>
</head>
<body>
<script style="javascript">
var xmlHttp;
//异步刷新验证码
function reload() {
//针对不同浏览器，不同的方式生成xmlHttp对象
try{
xmlHttp=new XMLHttpRequest();
}catch(e){
try{
xmlHttp=new ActiveXObject("Msxml2.XMLHttp");
}catch(e){
try{
xmlHttp=new ActiveXObject("Microsoft.XMLHttp");
}catch(e){
alert("你的浏览器不支持AJAX") ;
return false;
}
}
}
var url="ValidateCodeServlet";
xmlHttp.onreadystatechange = deal;//该属性为一个函数
xmlHttp.open("GET", url, true);//初始化xmlHttp
xmlHttp.send(null);//发送
}
function deal(){
if(xmlHttp.readyState==4){//当状态值为4时，接收到服务器传输的信息
//重新从servlet获得图片资源，并且防止浏览器缓存，加了时间
document.getElementById("validate_code").src = "ValidateCodeServlet?" + new Date().getTime();
}
}
</script>
<form method="post" action="check.jsp">
<input type="text" name="input_code"/>
<img src="ValidateCodeServlet" id="validate_code"/>
<a href="#" onclick="reload()">看不清楚，换一个</a>
<input type="submit"/>
</form>
</body>
</html>

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8"/>    <title>验证码测试</title></head><body><script style="javascript">    var xmlHttp;    //异步刷新验证码    function reload() {        //针对不同浏览器，不同的方式生成xmlHttp对象        try{            xmlHttp=new XMLHttpRequest();        }catch(e){            try{                xmlHttp=new ActiveXObject("Msxml2.XMLHttp");            }catch(e){                try{                    xmlHttp=new ActiveXObject("Microsoft.XMLHttp");                }catch(e){                    alert("你的浏览器不支持AJAX")   ;                    return false;                }            }        }        var url="ValidateCodeServlet";        xmlHttp.onreadystatechange = deal;//该属性为一个函数        xmlHttp.open("GET", url, true);//初始化xmlHttp        xmlHttp.send(null);//发送    }    function deal(){        if(xmlHttp.readyState==4){//当状态值为4时，接收到服务器传输的信息            //重新从servlet获得图片资源，并且防止浏览器缓存，加了时间            document.getElementById("validate_code").src = "ValidateCodeServlet?" + new Date().getTime();        }    }</script><form method="post" action="check.jsp">    <input type="text" name="input_code"/>    <img  src="ValidateCodeServlet" id="validate_code"/>    <a href="#" onclick="reload()">看不清楚，换一个</a>    <input type="submit"/></form></body></html>

2.check.jsp，用来判断用户表单提交的验证码是否正确，也是较为简单的Java代码。

[html] view plain copy

print?

<%@ page contentType="text/html;charset=UTF-8" pageEncoding="UTF-8" language="java" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<html>
<head>
<title>检验验证码</title>
</head>
<body>
<%
String code = (String) session.getAttribute("code");
String input_code = request.getParameter("input_code");
if (code != null && input_code != null) {
input_code = input_code.toUpperCase();
if (code.equals(input_code)) {
out.print("验证码正确");
} else {
out.print("验证码错误");
}
}
%>
<a href="index.html">返回填写页面</a>
</body>
</html>

<%@ page contentType="text/html;charset=UTF-8" pageEncoding="UTF-8" language="java" %><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%><html><head>    <title>检验验证码</title></head><body><%    String code = (String) session.getAttribute("code");    String input_code = request.getParameter("input_code");    if (code != null && input_code != null) {        input_code = input_code.toUpperCase();        if (code.equals(input_code)) {            out.print("验证码正确");        } else {            out.print("验证码错误");        }    }%><a href="index.html">返回填写页面</a></body></html>

3.ValidateCodeServlet，生成验证码图片的文件，代码中有详细的注释。

[java] view plain copy

print?

package com.yykj.servlet;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
public class ValidateCodeServlet extends HttpServlet {
private Random random = new Random();
private String[] allCodes = {
"0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
"A", "B", "C", "D", "E", "F", "G", "H", "I",
"J", "K", "L", "M", "N", "O", "P", "Q", "R",
"S", "T", "U", "V", "W", "X", "Y", "Z"
};
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.setHeader("Pragma", "No-cache");
resp.setHeader("Cache-Control", "No-cache");
resp.setDateHeader("Expires", 0);//禁止客户端缓存页面
resp.setContentType("image/jpg");//设置响应正文类型为图片
int height = 20;
int width = 60;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();//获取处理图片的画笔
g.setColor(getRandomColor(200, 250));//设置背景色
g.fillRect(0, 0, width, height);//画一个矩形
g.setFont(new Font("Times New Roman", Font.PLAIN, 18));//设置字体
g.setColor(getRandomColor(160, 200));//设置干扰线的颜色
for (int i = 0; i < 100; i++){//画一百条干扰线
int x = random.nextInt(width);
int y = random.nextInt(height);
int x1 = random.nextInt(10);
int y1 = random.nextInt(10);
g.drawLine(x, y, x1, y1);//干扰线的两个顶点坐标
}
String strCode = "";
for (int i = 0; i < 4; i++){//生成四个随机字符
String strNumber = allCodes[random.nextInt(36)];
strCode += strNumber;
g.setColor(getRandomColor(20, 120));
g.drawString(strNumber , 13 * i + 3, 16);
}
req.getSession(true).setAttribute("code", strCode);//将生成的验证码存入session
g.dispose();//释放图像的上下文资源
ImageIO.write(image, "JPEG", resp.getOutputStream());//输出JPEG格式图像
resp.getOutputStream().flush();//刷新输出流
resp.getOutputStream().close();//关闭输出流
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
//生成随机RGB颜色
private Color getRandomColor(int min, int max){
int r = min + random.nextInt(max - min);
int b = min + random.nextInt(max - min);
int g = min + random.nextInt(max - min);
return new Color(r, b, g);
}
}

package com.yykj.servlet;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.http.*;import java.awt.*;import java.awt.image.BufferedImage;import java.io.IOException;import java.util.Random;public class ValidateCodeServlet extends HttpServlet {    private Random random = new Random();    private String[] allCodes = {        "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",            "A", "B", "C", "D", "E", "F", "G", "H", "I",            "J", "K", "L", "M", "N", "O", "P", "Q", "R",            "S", "T", "U", "V", "W", "X", "Y", "Z"    };    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        resp.setHeader("Pragma", "No-cache");        resp.setHeader("Cache-Control", "No-cache");        resp.setDateHeader("Expires", 0);//禁止客户端缓存页面        resp.setContentType("image/jpg");//设置响应正文类型为图片        int height = 20;        int width = 60;        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);        Graphics g = image.getGraphics();//获取处理图片的画笔        g.setColor(getRandomColor(200, 250));//设置背景色        g.fillRect(0, 0, width, height);//画一个矩形        g.setFont(new Font("Times New Roman", Font.PLAIN, 18));//设置字体        g.setColor(getRandomColor(160, 200));//设置干扰线的颜色        for (int i = 0; i < 100; i++){//画一百条干扰线            int x = random.nextInt(width);            int y = random.nextInt(height);            int x1 = random.nextInt(10);            int y1 = random.nextInt(10);            g.drawLine(x, y, x1, y1);//干扰线的两个顶点坐标        }        String strCode = "";        for (int i = 0; i < 4; i++){//生成四个随机字符            String strNumber = allCodes[random.nextInt(36)];            strCode += strNumber;            g.setColor(getRandomColor(20, 120));            g.drawString(strNumber , 13 * i + 3, 16);        }        req.getSession(true).setAttribute("code", strCode);//将生成的验证码存入session        g.dispose();//释放图像的上下文资源        ImageIO.write(image, "JPEG", resp.getOutputStream());//输出JPEG格式图像        resp.getOutputStream().flush();//刷新输出流        resp.getOutputStream().close();//关闭输出流    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }    //生成随机RGB颜色    private Color getRandomColor(int min, int max){        int r = min + random.nextInt(max - min);        int b = min + random.nextInt(max - min);        int g = min + random.nextInt(max - min);        return new Color(r, b, g);    }}

注意：ValidateCodeServlet要在web.xml中配置，配置代码如下：

[html] view plain copy

print?

<servlet>
<servlet-name>ValidateCodeServlet</servlet-name>
<servlet-class>com.yykj.servlet.ValidateCodeServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ValidateCodeServlet</servlet-name>
<url-pattern>/ValidateCodeServlet</url-pattern>
</servlet-mapping>

  <servlet>    <servlet-name>ValidateCodeServlet</servlet-name>    <servlet-class>com.yykj.servlet.ValidateCodeServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>ValidateCodeServlet</servlet-name>    <url-pattern>/ValidateCodeServlet</url-pattern>  </servlet-mapping>

以上是关于jsp页面该如何刷新验证码的主要内容，如果未能解决你的问题，请参考以下文章

验证码

JSP页面中验证码的调用方法

c# Winform 实现登录界面验证码功能（文末附源码）

动态生成能够局部刷新的验证码AJAX技术---看了不懂赔你钱

收不到“易来通”健康码的验证码？试试刷新

JSP生成验证码